Generally in normal bone metabolism, bone resorption by osteoclasts and osteogenesis by osteoblasts are balanced, whereby homeostasis is maintained. It is presumed that diseases associated with bone metabolism develop when the balance between bone resorption and osteogenesis is disrupted. Such diseases include osteoporosis, osteitis fibrosa (hyperparathyroidism), osteomalacia, Paget's disease, and the like. Particularly, osteoporosis often develops in postmenopausal women and elderly people with accompanying symptoms of pain such as lower back pain, bone fracture, etc. For such diseases associated with bone metabolism, hormone replacement therapies with estrogen and therapeutic agents such as bisphosphonates and calcitonins, both of which inhibit the activity of osteoclasts, have been employed.
Although many of these therapeutic agents are reported to have a bone resorption-inhibiting action, etc., none of them has yet been clearly shown to have an osteogenesis promoting effect. Particularly, impaired osteogenic ability due to reduced bone turnover is reported to be the main cause of senile osteoporosis (Non-patent Literature 1), and thus a medicinal agent promoting osteogenesis is considered to be effective. In view of the above, development of a clinically highly effective, orally administrable osteogenesis promoter is demanded.
WO2009/101959 (Patent Literature 1) describes compounds as shown below, which however differ in structural features from the compound of the present invention.
